"During this very sad and difficult time, we have also had to turn our attention to our remaining 29 cats in our facility," said Dale Anderson, Cat Haven's founder. "It is important that we attend to their health and well-being, and we believe returning to a state of normal operations is a part of that process."

Cat Haven, located in Dunlap, Calif., will reopen to the public from 10 a.m. to 3 p.m. Sunday, according to a news release today.

The facility has been closed since Wednesday, when, at approximately 12:30 p.m., the intern, Dianna Hanson, 24, died of a broken neck when she was attacked by a lion, Fresno County Coroner David Hadden said Thursday.

It's still unclear why the lion attacked her.

Hadden told ABC News that he believed a gate or door may have been left partially open, allowing the 4-year-old male African lion named Cous Cous to attack Hanson.

"The cat had just been fed and there was food in the bowl and the cat had ignored the food in order to have access to this young lady," Hadden said Thursday night.

However, Fresno County Sheriff's Lt. Patrick Hanson told ABCNews.com Thursday night that police still were determining the circumstances of Dianna Hanson's death, and investigators "cannot confirm or deny which gates were working or which gates weren't working."

Hanson died instantly but Cous Cous caused additional wounds to the woman's body after her death.

"She did not suffer," Hadden said. "As tragic as this death is, it's important to know that she wasn't alive for a long time."

Hanson was reportedly talking on her cellphone with a co-worker at the time of the incident when the call abruptly ended, suggesting Hanson might have been completely caught off guard by the lion. The co-worker grew concerned when Hanson failed to call back, The Associated Press reported.

Another employee tried unsuccessfully to lure Cous Cous away from Hanson and into another enclosure.

Less than 30 minutes after Hanson entered the cage, Cous Cous was shot by a Fresno County sheriff's deputy who responded to a call, authorities said.

The body of the 500-pound lion was taken to a vet facility in Tulare County for a necropsy to determine what may have caused the fatal attack.

Hanson was two months into an internship program at the Cat Haven in Dunlap, a small town in Fresno County near King's Canyon National Park, when she was killed.

"Even though she was only with us for a little over two months, she was part of our family," said Wendy Debbas, the president of Project Survival Cat Haven, a non-profit group associated with the sanctuary, on Thursday. "She made instant friendships with everybody up here. Everybody loved her.

"She has songs she made up for each of the cats," Debbas told reporters. "A cute example of that is we have jaguar cubs named Samba and Rose. Samba's song was not 'La Bamba' but 'La Samba.' And Rose was 'Kissed by a Rose.' And she had songs like that for all of the cats. She was vivacious. She loved her work. She loved big cats."

Hanson's father said Thursday that she never feared working with big cats, but he always feared something might happen to her.

"Anybody who works with cats knows that they are wild animals and they can turn even on people closest to them," Hanson's father, Paul Hanson, told ABC News. "So I always had this horrible, nagging premonition that I would get a call like this."

Hanson said his daughter loved to be around big cats and that working with them was her true passion in life.

Hanson's grief-stricken father is now left with the question of why his daughter was in the enclosure with the lion.

"How she ever got inside the cage and why she would be inside the cage [is unclear], because I thought she made it real clear that they don't let anybody in the cage except the owner," Paul Hanson said.

Cat Haven was founded in 1993 and is run by Project Survival, a privately funded education and conservation organization.

The 100-acre facility is home to a variety of wild cats -- including tigers, leopards and other threatened and endangered species that are kept for limited breeding and use in educational programs, according to Cat Haven's website.

Officials said the park has had a good history, and had an active permit to operate.

Cat Haven also runs an outreach program, and its "cat ambassadors" may sometimes be taken off-site to make appearances as part of that program, according to the website.

Hanson's mother, Donna Anderson, noted that she adopted a Siberian tiger in her daughter's name for her seventh birthday, helping to fund the research of tigers and maintenance of their natural habitat.

"Because of the stories that came through with that adoption process, she grew to understand that these beautiful cats in the wild are decreasing in numbers, and she wanted to do something to help that not happen," Anderson said.

Cat Haven noted in its announcement, "The family has asked that all donations be made to the charity of the donor's choosing. Donations can be made directly on the non-profit organizations' respective websites."